In a decoration of a general festival, stage or hall, for elevating the aesthetic feeling of an illumination source, a festoon lighting sets with multiple lamp holders is usually used, a double-headed lamp is placed into each lamp holder, and the festoon lighting set is respectively wound around ceilings, cupboards, display windows, tables and decorations to allow it to have a continuous long strip light source to attain to the illumination and decoration effects.
As FIGS. 1 and 2 show, two ends of a light bulb A11 of a conventional double-headed lamp structure are respectively put around with a metal engagement head A1 clipping tightly and connected to the light bulb A11 by means of adhesion, a terminal A13 is extended from each engagement head A12 and the terminal A13 is let in a retaining portion A21 of the lamp holder A2 to allow the double-headed lamp A1 to be fixed in the lamp holder A2 to use as an illuminating decoration after the power source is conducted, in which the light bulb A11 is illuminated by conducting electricity to heat tungsten filaments to be incandescent. Besides, the periphery of the light bulb A11 is made from glass and the light bulb A11 is in a vacuum state or filled with inert gas so as to prevent the tungsten filaments from being oxidized under a high temperature.
However, the power source used in the double-headed lamp A1 is AC or DC and the light bulb A11 is taken as an illumination material; this not only shorten the life of the double-headed lamp A1 but also cause it to have the deficits of electricity consumption and high temperature. Besides, not only it needs to process manufacturing more than twice to couple the engagement head A12 to the light bulb A11 but also the engagement head A12 is unable to be coupled to the light bulb A11 tightly to cause the production cost to be higher and the fraction defective not to be lowered down. Moreover, the light bulb A11 of the double-headed lamp A1 is unable to provide various colors to cause the decoration effect to be limited and consequently, the use of the double-headed lamp is limited.